Small internal combustion engines such as commonly used on lawn mowers and the like often utilize rope-operated recoiling starters. Such starters basically include a pulley upon which a starter rope is wound, a driving member or gear associated with the pulley which engages engine flywheel structure when the pulley is rotated in an engine cranking direction, and a recoil spring associated with the pulley to automatically rewind the rope thereon upon releasing the rope tension.
A wide variety of rope-operated recoil starters have been produced, and a popular construction has been a starter of the Bendix type wherein a bracket is mounted upon the engine adjacent the engine flywheel supporting a shaft upon which a rope pulley is rotatably mounted. The pulley includes a groove receiving a rope wound therein, and the pulley structure includes a hub having a helical or spira1 spline or thread defined thereon. A driving member in the form of a gear is mounted upon the hub and includes a bore having spiralled splines complementary to those of the pulley hub. The periphery of the gear includes clutch structure, usually gear teeth, engagable with clutch structure, often gear teeth, defined on the engine flywheel upon translation of the gear between a retracted position and a cranking position. Axial translation of the gear between the retracted and cranking positions is controlled by a friction brake tending to retard rotation of the gear. As the retarding of gear rotation produces relative rotation between the pulley and the gear, the friction brake controls the axial translation of the gear on the pulley hub.
Examples of the aforedescribed type rope recoil starter are shown in U.S. Pat. Nos. 3,375,813; 3,465,740; 3,827,307; 3,906,921; 3,942,505 and 4,167,929.
The friction brake associated with the driving member or gear often consists of a resilient wire embracing a groove defined in the gear. A radial extension formed on the brake engages a fixed abutment usually defined on the mounting bracket and the friction brake is restrained against rotation whereby the gear will be continually restrained against rotation during all of the starter cycles of operation. U.S. Pat. No. 3,827,307 discloses a brake operator which reduces the frictional braking action at predetermined angular positions of the brake.
Due to the heavy vibration present in a small internal combustion engine, the vibration may cause the starter gear to rotate or "creep" relative to the pulley hub during normal engine operation. This gear rotation is due to the vibration overcoming the resistance to gear rotation produced by the friction brake, and the gear may axially translate on the pulley hub sufficiently to inadvertently contact the rotating engine flywheel starter clutch or gear teeth, with the possibility of damaging or excessively wearing the flywheel or starter components. Lockout means for the gear to prevent engagement with the engine flywheel are shown in U.S. Pat. Nos. 3,906,921 and 3,942,505, but such lockout structure is for the purpose of preventing starter operation when the lawn mower wheel drive apparatus is in engagement, and such lockout apparatus as shown in these patents will not prevent "creep" of the gear due to engine vibration, when drive is not engaged.
For safety purposes it is now required in some jurisdictions that rotary lawn mowers mount the engine starter rope handle on the mower handle. Such location of the starter rope handle requires that the operator stand behind the mower handle remote from the mower engine and blade during starting. As such an installation requires the starter rope to extend from the engine to the mower handle several problems are produced not previously encountered with conventional starter installations wherein the rope handle is located adjacent the engine and engine-mounted starter structure. For instance, lawn mower handles are usually capable of limited pivotal movement with respect to their connection to the mower deck and such pivotal mower handle movement will produce tension, or slack, in the starter rope mounted thereon. Thus, a pivoting of the mower handle which tensions the starter rope would produce movement of the starter gear toward the engine flywheel causing engagement therebetween while the flywheel was rotating.
Another problem created by the mounting of the starter rope handle upon a lawn mower handle results from the need for a greater length of starter rope than previously required in that the rope handle is now located at a considerable distance from the starter pulley. As starters and engines are usually sold to lawn mower manufacturers as an assembled unit, the extra rope required creates a problem prior to the rope handle being mounted on the lawn mower handle and handling, painting and assembly difficulties have been encountered.
One approach toward overcoming the problems relative to mounting the starter rope handle on the lawn mower handle has been to locate a knot, or other abutment, on the starter rope for engagement with a stop after a predetermined recoiling of the starter rope upon its pulley has occurred. This restraint of the recoiling of the starter rope permits slack to exist between the starter and the starter rope handle so that the pivotal movement of the lawn mower handle does not produce a rotation of the rope pulley. However, this solution to the problem results in an unsightly and loose starter rope, increases the likelihood of starter rope kinking and damage thereto, and complicates the assembly or replacement of the starter and starter rope on the lawn mower.
It is an object of the invention to provide a rope recoil starter particularly suitable for lawn mower use where the rope pull handle is mounted upon the lawn mower handle wherein a delay exists in the axial translation of the driving element or gear toward the engine flywheel after the initial rotation of the rope pulley in a cranking direction.
Another object of the invention is to provide a rope recoil starter of the Bendix type utilizing a friction brake to axially translate a starter gear wherein lost motion means are associated with the friction brake to delay translation of the gear toward the engine starting structure during rotation of the rope pulley in a cranking direction.
An additional object of the invention is to provide a rope recoil starter of the Bendix type having a positive gear lockout preventing inadvertent engagement of the starter gear and engine starting structure due to movement of the gear due to engine vibration.
A further object of the invention is to provide a rope recoil starter having a rope wound upon a pulley wherein access to the rope inner end is provided to simplify rope replacement.
Another object of the invention is to provide a rope recoil starter pulley of such configuration wherein the pulley includes rope storage structure upon which extra rope may be wound during handling and shipping of the starter and associated engine to simplify assembly of the starter components to the handle of a lawn mower, and also, provide extra rope for cranking, if desired.
Yet another object of the invention is to provide a rope recoil starter including a rope pulley mounted upon a shaft wherein a shaft mounted cover functions to enclose a pulley recoil spring and includes a cylindrical skirt disposed over the rope receiving groove and a pulley storage portion for excess rope to improve confinement and alignment of the starter rope upon the pulley.
In the practice of the invention a sheet metal bracket is mounted upon the internal combustion engine adjacent the engine flywheel. A shaft is supported upon the bracket at one end, and a rope pulley is rotatably mounted upon the shaft. The rope pulley includes a radial rope receiving groove in radial alignment with the outer region of the shaft, and a pulley hub surrounds the majority of the shaft and is located between the rope groove pulley portion and the bracket. Helically spiralled splines are defined on the outer surface of the pulley hub.
An annular cover is mounted upon the outer end of the shaft and includes a radial wall encompassing a spiral spring, one end of which is attached to the cover, and the other end is affixed to the pulley for rotating the pulley in the rope recoiling direction. The rope groove is of a width substantially equal to the diameter of the rope, and at its outer region, the rope groove includes a cylindrical land upon which excess rope may be wound prior to completion of the assembly of the starter with the lawn mower with which it is associated.
A driving member in the form of a gear is mounted upon the pulley hub, and the gear bore is provided with helical splines complementary to those defined on the pulley hub wherein relative rotation between the gear and hub axially translates the gear between a retracted position and an extended engine cranking position. Teeth defined on the gear periphery are adapted to engage gear teeth defined on the engine flywheel upon the gear being located in the cranking position.
A friction brake formed of wire embraces a groove defined on the gear. The friction brake includes a radial extension, and the purpose of the brake is to retard rotation of the gear to produce relative rotation between the pulley and gear to axially translate the gear.
A pair of stops or abutments are defined on the starter bracket radially spaced from the shaft and are located, in the disclosed embodiment, at substantially diametrically opposed positions with respect to the shaft. The abutments are formed from the metal of the bracket, and are located relative to the shaft for engagement with the brake radial extension. The brake extension is located between the abutments for rotation or oscillation therebetween, rotation of the rope pulley in one direction causing the extension to engage one abutment, while rotation of the pulley in the opposite direction causing the friction brake extension to engage the other abutment. The friction brake will rotate through approximately 180.degree. between engagement with the abutments.
The starter mounting brakcet is also provided with a lockout ridge which is defined of the metal of the bracket. The ridge is of an arcuate configuration substantially extending between the brake extension engaging abutments and in axial alignment with the abutment movement whereby the brake abutment will engage the ridge during much of its movement, and such engagement will prevent axial displacement of the gear toward the engine flywheel. The ridge defined on the bracket terminates short of the abutment engaged by the brake extension when the pulley is rotated in the engine cranking direction for permitting the gear to move into engagement with the teeth of the engine flywheel and produce cranking. When the pulley is rotated in the recoil direction, axial movement of the gear toward its retracted position lifts the brake extension permitting the extension to rotate over an end of the ridge as the pulley continues to rotate in the recoil direction.
The cover mounted upon the end of the shaft includes a cylindrical skirt at its periphery which axially extends over the pulley rope groove and rope storage land. The cover skirt includes an opening through which the rope extends, but as the skirt encompasses the majority of the circumference of the pulley it confines the rope within the pulley and minimizes rope groove and rope alignment problems during recoiling, especially if the tension on the rope has been excessively released during recoiling.
The aforementioned features permit a delay in the gear movement with respect to rotation of the starter pulley, and such delay prevents inadvertent starter and flywheel engagement due to pivoting of the lawn mower handle. The use of the ridge prevents inadvertent engagement of the starter gear and flywheel due to vibration, and these important features of the invention can be produced without requiring expensive and complex machine or assembly techniques.